Textile process which uses concentrated sulfuric acid after resin treatment



United States Patent ice 3,515,505 TEXTILE PROCESS WHICH USESCONCENTRATED SULFURIC ACID AFTER RESIN TREATMENT Hans Kraessig andRicardo Bellvila, Schwerzenbach, Switzerland, assignors, by mesneassignments, to Heberlein & C-o. A.G., Wattwil, St. Gall, Switzerland, acorporation of Switzerland No Drawing. Continuation-impart ofapplication Ser. No. 470,895, July 9, 1965. This application Dec. 14,1965, Ser. No. 513,812 Claims priority, application Switzerland, July10, 1964, 9,094/ 64 Int. Cl. D06m 13/12 U.S. Cl. 8116.3 16 ClaimsABSTRACT OF THE DISCLOSURE The instant invention is concerned with aprocess in which textile materials are treated with resin precondensate,dried below the curing temperature, and then treated with an aqueoussolution of concentrated sulfuric acid to fix the precondensate andremoving the acid.

This is a continuation-in-part of our copending application Ser. No.470,895, now abandoned, filed July 9, 1965.

This invention relates to a textile process and the products produced bythe process, and more particularly, it relates to a process whichimparts crease-resistance to fabrics and further it relates to fabricswhich can be treated to make them crease-resistant after they have beenmanufactured into articles of apparel and the like.

The processes for finishing cellulosic textile materials with resins arewell-known. In one process a resin precondensate and a catalyst areapplied to a textile material and subsequently cured under the influenceof heat. Another known process for resin-finishing cellulosic textilematerial involves applying a solution of a polymerizable synthetic resinand a catalyst to the textile material, predrying the material at atemperature below the curing temperature, manufacturing articles ofapparel and the like from the predried material and changing the form ofthe material, such as for example by adding folds or pleats, andsubsequently polymerizing the synthetic resin under the influence oftemperatures above about 100 C. to produce a crease-resistant finishedarticle. This type of process has become known in the textile industryas deferred curing.

It is also known to condense resin precondensates on cellulosic textilesunder the influence of sulfuric acid, as for example by treating thematerial in strongly acidified baths, to produce a finishedcrease-resistant cellulosic textile. This operation is carried out witha comparatively weak sulfuric acid concentration and after treatment inthe acidified precondensate bath the material is subsequently stored fora comparatively long reaction period. This prior art process produces acompletely cured textile by means of the one-bath treatment andsubsequent storage.

It would be desirable to provide a process in which cellulosic materialscan be made crease-resistant after they have been formed into thefinished article. In such a process the desired pleating, folding, andforming could be performed directly on the article made from thetextile. It is of course possible to make articles from acellulose-containing textile which is already crease-resistant, but itis frequently diflicult or inconvenient to put permanent folds, pleatsand creases into these articles at the desired place after the resintreatment. It would be possible to treat the finished article withconventional resin precondensates after manufacture, but this wouldPatented June 2, 1970 require that clothing manufacturers have chemicaltreating equipment, and would generally only be satisfactory for verylarge users. Moreover, there would be a limited range of treatmentavailable, and many finishing agents could not be utilized.

This invention provides a method for producing cellulosic textilematerials which can be made crease-resistant after fabrication intofinished goods.

This invention also provides a method by which the manufacturer canproduce crease-resistant cellulosic fabrics solely by the application ofheat so that such materials can be formed into finished articles andthen rendered crease-resistant.

Further and more specific objects, features, and advantages will clearlyappear from the detailed description given below.

Briefly, the process of this invention for finishing textiles involves,first, the application of a resin precondensate to a cellulosic textilematerial and then drying the material, treating the dried material withaqueous sulfuric acid to fix the resin precondensate to the textilematerial and produce a material which can be cured in the presence of acatalyst to provide a crease-resistant textile.

In some embodiments of this invention the process includes the furthersteps of drying the sulfuric acid treated textile and subsequentlycuring it, generally at temperatures in excess of C.

For purposes of this application, the terms textile material or fabricshall both be understood to include fabrics and textile materials of allkinds, including any manner of Woven or knit fabrics. Further, forpurposes of this application the term cellulosic textile material willbe understood to apply to any kind of fabrics containing cellulosicfiber material, and includes fabrics in which cellulosic materialsconstitute a significant proportion. This term includes mixed fabricsconsisting of cellulose in admixture with other natural or syntheticfibers. Especially preferred cellulosic textile materials are those madefrom natural cellulose such as cotton, regenerated cellulose such asviscose rayon, or chemical derivatives of cellulose such as acetaterayon. Additionally, mixtures of natural cellulose with regeneratedcellulose or chemical derivatives of cellulose are comprehended bycellulosic textile materials.

Suitable resin precondensates for use in the process of this inventionare all the precondensates used in the textile-finishing art. Forexample, precondensates consisting of formaldehyde and a nitrogenousmaterial can be used in this invention. Desirable nitrogenous materialsare, for example, urea or thiourea and their derivatives, especially thecyclic derivatives of urea in the form of heterocyclic fiveorsix-membered ring compounds, and also bicyclic compositions such as theso-called acetylene-diurea. Moreover the nitrogenous material can be acarbamate derivative or a triazine derivative, and particularly melaminederivatives and the like or, generally, amino methylol compounds.

In one aspect of this invention, it is especially preferred to usesubstances which react at acid pH with the cellulose, or with themselvesand the cellulose, to cross-link the cellulose. Examples of desirablecompounds are acetals, epoxides, polyepoxides, halohydrins, and methylolcompounds, for example precondensates of formaldehyde and a compoundhaving interchangeable hydrogen atoms, as for example the methylolcompounds of ketones and of urea, thiourea, and their derivatives. It isespecially preferred to use cyclical urea derivatives in the form ofheterocyclic fiveor six-membered ring compounds and their hydroxy or oxoderivatives. It is also advantageous to use bicyclic hetero compoundssuch as the so-called acetylene-diurea, dicyandiamide, guanidine, orcarbamates and the like. Moreover, triazine derivatives such asderivatives of melamine and their etherification products can be used.Also useable are mixtures of such products commonly used in the textilefinishing art.

The resin precondensates can be applied to the cellulosic textilematerials in various forms and by various techniques. For example, theresin precondensates can be applied to the cellulosic textile materialfrom aqueous solutions, suspensions, or dispersions or from solutions,suspensions, or dispersions of the precondensate in other solvents orvehicles. The precondensate can be applied to the cellulosic textilematerial by dipping, padding, spraying, and other means of impregnatingthe material uniformly with the precondensate.

The cellulosic textile material is subsequently dried after impregnationwith the precondensate. It will be understood that the term dryingincludes the removal of a substantial portion of the solvent or vehiclefrom the material. It will be further understood that the drying takesplace at a temperature which is sufficiently low to obviate anysignificant amount of curing of the precondensate. The cellulosictextile material is treated with the amount of precondensate customarilyused in the production of crease-resistant textiles. The drying isordinarily carried out at temperatures below 100 C. to a final moisturecontent no greater than the equilibrium moisture of the textile inambient air.

The step subsequent to this drying step is the one which partially fixesthe precondensate onto the cellulosic textile material to provide theoutstanding advantages of this invention. This partial fixing orprefixing of the resin precondensate by means of the sulfuric acidapparently binds a number of the reactive groups of the resin to thecellulose, while sufficient reaction groups remain free, so that theresin can be completely cured by heating in the presence of a catalysthaving a potential acid reaction. Such curing may take place after thematerial has been changed in form, for example, by manufacture ofapparel or other articles from the fabric.

In distinction to the prior art processes above men tioned, thisinvention partially binds the precondensate to the cellulosic materialunder the influence of the sulfuric acid. This partial fixation isreadily detectable among other criteria, by the fact that it isimpossible to wash out the prefixed resin from the textile material.Moreover, a material, for example, a cotton fabric, already shows evenin this intermediate stage a very high wet creaseangle. However, it hasbeen surprisingly found that the sulfuric acid treatment of this processpermits the retention of sufficient free reactive groups in the resinprec ndensate to allow a complete cure of the resin merely by heating itin the presence of a condensation catalyst.

Thus contrary to expectations from consideration of prior art sulfuricacid treatments, the process of this invention does not result directlyin the final crease-resistant product, but rather an intermediateproduct is first obtained in which the resin is bound to the cellulose,but still retains sufficient free reactive groups to be cured completelyin a later reaction step. Thus, this invention provides textilematerials which can be changed in form and then subsequently permanentlyfixed during final curing of the textile. For example, between thetreatment with the precondensate and the final curing step folds andcreases can be set into the finished article after fabrication.

The textile materials of this invention are capable of being readilyworked and formed into finished articles Without the necessity forspecial care to cut the fabric along such lines as to maintain thecreases previously permanently set into the fabric and without thenecessity to attempt to impregnate finished articles evenly withprecondensates and then to fix them. Indeed, this latter procedure wouldbe impractical because the treatment with the precondensate has atendency to take out any creases or folds which have formed in thearticle.

The sulfuric acid treatment of this invention is carried out bycontacting the dried textile material which has previously beenimpregnated with the precondensate with sulfuric acid having aconcentration of from about 40 to about 60% H The treatment perioddesirably ranges from about half a minute to about thirty minutes. Sincethe process of this invention is particularly adapted to continuousoperation, it is preferred to contact the material with the sulfuricacid for a time of from about one to about ten minutes. It is especiallypreferred to utilize sulfuric acid strengths in the range of from about50 to about H Unless otherwise indicated, all parts, percentages, andproportions herein are by Weight. 5

After the sulfuric acid treatment step, the acid is completely removedfrom the material by washing and/or neutralization, as with aqueousalkali, and the material is dried. At this stage it will be found th atthe resin is already fixed on the cellulose, but only partially so thatsufiicient active groups remain to allow cross-linking under theinfluence of later treatment. After this. sulfuric acid treatment thetextile material of this invention is ready for further processing, asfonexample by the manufacture of clothing and articles of a@areltherefgrn Before or after the garment or otherartifact has been formed,a curing catalyst is applied to the fabric. This can readily beaccomplished by padding, spraying, and the like. All catalystscustomarily used for resin curing, and especially ordinary acidcatalysts and those having a potential acid reaction, can be utilized.Combined catalysts offered by the trade can also be used. Especiallysuitable for use in this process are salts which have a neutral reactionat ordinary temperatures, but possess an acid reaction at curingtemperatures, as disclosed below. Examples of suitable catalysts aremagnesium chloride, ammonium chloride, monoammonium phosphate, zincchloride, zinc nitrate, magnesium perchlorate, zinc fluoborate and thelike.

After treatment with the catalyst, the resin cure is completed by heattreatment at temperatures in excess of C. It is preferred to carry outthe curing at temperatures in the range of from about to about 180 C.,desirably over a period of from about one to about ten minutes. Thiscuring can be carried out in any desired manner, such as by heating inan oven or in a press. It will be found that any changes in form whichhave been made on the finished article, such as folds or pleats, Will bepermanently fixed into the finished article, whereas the remainder ofthe fabric exhibits little or no creasing and dries smoothly.

During the treatment with catalyst and curing, the cellulose is in anon-swollen condition, as opposed to its swollen condition duringtreatment with the sulfuric acid. Thus, this second trearnent especiallyimproves the drycrease angles. This behavior confirms the fact thatreactivi1 groups remain even after treatment with the sulfuric aci Inanother aspect of this invention a resin precondensate is added to thecatalyst solution further to enhance the crease resistance of materialonto which a precondensate has already been fixed by means of sulfuricacid. Relatively small quantities of these materials which are capableof reacting with cellulose or with themselves and cellulose are added inthis stage of the process. The resin precondensates as set forth aboveare suitable for use in this aspect of the invention.

The following examples are given to illustrate the practice of thisinvention, but it will be understood that these examples do not limitthe scope of the invention, the scope being determined by the claimsappended hereto.

EXAMPLE I A cotton poplin fabric is padded with a solution of g./l. ofLyofix CH melamine-formaldehyde precondensate manufactured by Ciba Ltd.of Basel, Switzerland. The fabric is then predried and treated in a bathof 57% sulfuric acid for three minutes, briefly rinsed in water,neutralized with a dilute soda solution, and thoroughly rinsed.

After any desired time interval and treatment a solution containing 20g./l. of Catalyst PR curing catalyst is sprayed onto the fabric so thatabout 1.01.5% by weight (based on the dry fabric) of the catalyst isdeposited as uniformly as possible on the fabric. This fabric can besubjected to garment finishing operations and then renderedcreas-resistant by a high-temperature treatment to cure it.

EXAMPLE II A cotton poplin fabric is padded with a solution of 150 g./l.of 50% 4,5-dihydroxy-1,3-dimethylolethylene urea so as to depositapproximately 0f the urea on the fabric. After predrying, the fabric istreated with a 57.0% sulfuric acid solution for three minutes andthoroughly rinsed with water. Subsequently, the fabric is padded with acatalyst solution consisting of 15 g./l. of MgCl .6H O and dried to afinal moisture content of 810%.

Thereupon the fabric is manufactured into finished clothing and folds orpleats are applied as desired to the treated fabric. The treated fabricis then rendered Washproof by curing for five minutes at 145-150 C.while the remainder of the fabric is Wash-and-wear finished, that is, itis smooth-drying.

EXAMPLE HI A cotton fabric is padded with a solution of 300 g./l. of 50%dimethylol methylcarbamate and dried. Subsequently the padded and driedfabric is brought into contact with a dilute sulfuric acid solutioncontaining 54% sulfuric acid for ten minutes. The sulfuric acid is thencompletely washed out of the fabric, first by neutralization with analkali and then by thoroughly rinsing. Subsequently a solutioncontaining 10 g./l. of zinc nitrate and 30 g./l. of a conventional 50%ethyleneureaforrnaldehyde precondensate is padded onto the fabric anddried again.

Fabrics pretreated in this manner can be processed at a subsequent timeto obtain articles of apparel and folds can be made in the fabric ifdesired. The articles of apparel are cured in an ironing press at atemperature of 160170 C. for approximately five minutes by which meanswashproof folds are permanently fixed in the fabric and improvedcrease-resistance achieved.

EXAMPLE IV A cotton fabric is padded with 150' g./l. of =Fixapret CPdimethylol dihydroxyethyleneurea, manufactured by Badische Anilin &Sodafabrik AG of Ludwigshafen, Germany, and predried. This precondensateis fixed by treatment for eight minutes in a sulfuric acid bathcontaining 55% sulfuric acid.

After having been thoroughly washed out and dried the fabric is paddedwith an aqueous solution containing 75 g./l. of Fixapret PH dimethylolpropylene urea and 7.5 g./l. of Zinc nitrate, and dried to a residualmoisture of about This fabric is processed toarticles of apparel andpress-in folds are permanently fixed by subsequent heat treatment at 140C. for six minutes. Improved crease angles are also obtained.

EXAMPLE V A spun-rayon imitation linen fabric is padded with a solutionof 150 g./l. of a conventional tetramethylol acetylene diurea resin andpredried. The resin is fixed by treating the fabric in a 52% H 80 bathfor two minutes. The fabric is thoroughly rinsed and dried.

To produce articles of apparel at a later time, a solution containing amixture of a propylene urea formaldehyde precondensate and magnesiumchloride in a proportion of 5:2 is sprayed onto the fabric until 1.4% ofmagnesium chloride (based on the weight of the fabric) is applied. Afterthe manufacture of articles of apparel 6 and possibly pressing-in offolds, curing is completed by heating at 125-140 C. for ten minutes.

This treatment produces pressed-in folds that are fixed at the same timeas the crease resistance of the fabric is improved.

EXAMPLE VI A blended fiber fabric consisting of 65% cotton and 35%polyester staple fibers is padded with 140 g./l. of a precondensateproduced from urea and glyoxal by methylolizing and then dried. Thefixing is effected by treatment in a 56.0% H SO bath for three minutes.The acid treated material is then Washed until a neutral reaction isobtained.

After an intermediate drying the fabric is immersed in aqueous solutioncontaining g./l. of ethylene ureaformaldehyde precondensate (50%strength) and 8 g./l. of zinc nitrate and squeezed to an add-on of 65%.Subsequently the fabric is dried to a residual moisture of approximately12% and in this condition the fabric is prepared for the manufacture ofgarments. If creases are applied, a final treatment by heating at 150 C.for five minutes is sufficient to render the fabric wash-proof andsimultaneously improve the dry crease-angles. In this process the wetcrease angles have already been considerably increased after thesulfuric acid treatment.

The treatment with precondensate and sulfuric acid produces very highwet-crease angles with only slight losses in tensile strength. Thedry-crease angle, as disclosed above, is materially improved by thesubsequent curing in the presence of catalyst and (optionally)additional precondensate. Accordingly, the treatment with precondensateand sulfuric acid as set forth above followed by treatment with thecatalyst (and optional precondensate) and curing produces very highwet-crease angles and improved dry-crease angles with relatively lowlosses in tensile strength. This is further illustrated in the followingexamples.

EXAMPLE VII Part A Cotton poplin is padded with an aqueous solution of140 g./l. Lyofix CH melamine-formaldehyde precondensate. The squeezingeffect amounts of 70%. After predrying the textile fabric is immersed ina 58.0% solution of sulfuric acid at 20 C. for 4 minutes.

The textile fabric is then rinsed, neutralized with a 2% sodiumcarbonate solution and washed in running water until free from salt. Thetreated textile fabric shows a wet-crease angle of 150 (average valuefrom warp and weft) and a remaining tensile strength of 71%, whereas thedry-crease angle remains unchanged.

Part B A cotton poplin fabric is treated as described in Part A.Subsequently a solution of 2 g./l. Catalyst AC aliphatic aminehydrochloride, produced by Monsanto Chemical Company, is padded on thefabric, predried and cured at 145 to 150 during 5 minutes. The dry-,crease angle of the so treated fabric increases to (average value ofwarp and weft), the wet-crease angle is 145, and the remaining tensilestrength is 65 EXAMPLE VIII Cotton poplin fabric is treated as describedin Part A of Example VII. Subsequently a solution containing 20 g./l.commercial dimethylol-ethylene urea precondensate and 1 g./l. zincnitrate is padded onto the fabric. The fabric is predried and curedduring 5 minutes at 145 to 150. The dry-crease angle of the so treatedfabric increases to the remaining tensile strength amounts to 55%, andthe wet-crease angle is EXAMPLE IX Cotton poplin is padded with anaqueous solution of 70 g./l. tetramethylol-acetylene diurea andpredried. The

fabric is then passed through 57.0% sulfuric acid for three minutes andsubsequently washed until completely free of acid. This finishingresults in a wet-crease angle of the fabric of 165 (average value fromwarp and weft) and a remaining tensile strength of approximately 75%.The dry-crease angle is practically unchanged.

In the second stage the fabric is padded with an aqueous solution of 20g./l. tetramethylol-acetylene diurea and L g./l. of a commercial zincnitrate catalyst, dried, and cured at 150 C. The dry-crease angle is nowincreased from 55 to 100. The fiat-drying properties of this fabric areextremely good.

EXAMPLE X A cotton poplin fabric is padded with an aqueous solution ofcarbamate precondensate containing 100 g./l. dimethylol methylcarbamate. The precondensate is produced according to known methods fromtechnical methyl carbamate and formaldehyde at pH 11. After predryingthe fabric is subjected to a treatment with 60% sulfuric acid for 30seconds. After having washed the fabric free from acid and drying it, anaqueous solution of 10 g./l. Catalyst PR zinc nitrate made by Ciba ispadded onto it. The fabric is then dried and cured for /2 minutes.Subsequently the fabric is washed out and finished in the usual way. Thefabric shows considerably greater wetcrease angle of 170 (average warpand weft), a moderately increased dry-crease angle, and favorable fiatdrying properties.

EXAMPLE XI A cotton poplin fabric is impregnated with arr aqueoussolution of 70 g./l. tetramethylol acetylene diurea and picked upsolution to a 70% weight increase. After pre drying the fabric isimmersed in sulfuric acid containing 45.0% H 80 for 20 minutes andsubsequently washed to the neutral point. By this treatment the cottonfabric achieves a wet-crease angle of 156 at a minimum loss in tensilestrength of approximately The dry-crease angle is increased by anafter-treatment described in Example VIII, which also provides extremelygood fiatdrying properties of the fabric.

EXAMPLE XII A solution of 150 g./l. Knittex Everfit CR triazine mixedresin made by Pfersee G.m.b.I-I., Augsburg, Germany, is padded onto acotton poplin fabric. After drying the fabric is immersed in 56%sulfuric acid for eight minutes, rinsed, and washed free of acid. Afterredrying, the fabric is padded with a solution of 100 g./l.dirnethylolpropylene urea and 5 g./l. ammonium chloride, cured at 120for minutes, and washed out as usual. Samples of this fabric show thefollowing values as compared to the untreated materials:

Dry-crease wet crease Tensile angle angle strength Monsanto (deg.)(deg.) (k g.) values Untreated (control) 58 90 21. 0 1-2 Treated 117 154 12. 1 ie-5 EXAMPLE XIII Cotton poplin is padded with an aqueoussolution of 140 g./1. Lyofix OH and predried. It is then contacted with57% sulfuric acid for four minutes and thoroughly washed out. The dryfabric is then padded with a solution consisting of g./l. Fixapret AHdimethylol ethylene urea precondensate made by BASF, Ludwigshafen,Germany, 10 g./l. Catalyst PR, 6 g./l. of Cerol WB, astearylmethylamidomethylene pyridinium chloride made by Sandoz A. G.,Basel, Switzerland, and l g./l. Triton X 100 surface active agentproduced by Rohm & Hass, Philadelphia, Pa., predried', cured at for fiveminutes, and Washed out. The textile is found to have a dry crease angleof 145, a wet crease angle of 155, and extremely good flat-dryingproperties.

EXAMPLE XV A spun rayon linen imitation fabric (or spun rayon cretonne)is padded with an aqueous solution containing 250 g./l. Lyofix CH anddried. The fabric is then brought into contact with 50% sulfuric acidfor two minutes and is then thoroughly washed out and dried. The dryfabric is padded with an aqueous solution consisting of 100 g./l. of aurea formaldehyde precondensate (50%), 10 g./l. MgCl -6H O, and 5 g./l.polyvinyl alcohol, predried, cured at 145 to for 5 minutes, andsubsequently washed out. This treatment results in remarkably goodflat-drying properties.

What is claimed is:

1. A process for finishing textiles which comprises first applying aresin precondensate to a cellulosic textile material, drying thematerial at a temperature below 100 C., treating the dried material wtihan aqueous solution consisting essentially of sulfuric acid having aconcentration of from about 40% to about 60% H 80 to fix the resinprecondensate to the textile material and produce a material which canbe cured in the presence of a catalyst to provide a crease-resistantmaterial, and removing the sulfuric acid from the material.

2.. The process of claim 1 wherein a condensation catalyst is applied tothe material, after the sulfuric acid has been removed.

3. The process of claim 2 wherein the fixed precondensate is cured byheating to temperatures in excess of 100 C.

4. The process of claim 1 wherein the dried material is treated with anaqueous solution containing from about 40 to about 60% of sulfuric acidfor a period of from about 0.5 to about 30 minutes.

5. The process of claim 1 wherein the sulfuric acid is subsequentlyremoved from the material by neutralizing with an alkali.

6. The process of claim 1 wherein the precondensate consists essentiallyof formaldehyde and a nitrogenous compound.

7. The process of claim 6 wherein the nitrogenous compound is a cyclicurea selected from the group consisting of heterocyclic fiveandsix-membered rings.

8. The process of claim 6 wherein the nitrogenous compound is acarbamate.

9. The process of claim 6 wherein the nitrogenous compound is a triazinederivative.

10. A process for preparing finished artifacts which comprises firstapplying a resin precondensate to a cellulosic textile material, dryingthe material at a temperature below 100 C., treating the dried materialwith an aque ous solution consisting essentially of sulfuric acid havinga concentration of from about 40% to about 60% H 80 to fix the resinprecondensate to the textile material and produce a material which canbe cured in the presence of a catalyst to provide a crease-resistanttextile, removing the sulfuric acid from the material, forming anartifact, and curing the formed artifact by heating to temperatures inexcess of 100 C. in the presence of a condensation catalyst.

11. A process for finishing textiles which comprises first applying aresin precondensate to a cellulosic textile material, drying thematerial at a temperature below 100 C., treating the dried material withan aqueous solution consisting essentially of sulfuric acid having aconcentration of from about toabout H to fix the resin precondensate inthe textile material and produce a material Which can be cured in thepresence of a catalyst to provide a crease-resistant textile, removingthe sulfuric acid from the material, treating the material with acondensation catalyst, and finally curing the material by heating attemperature above about C.

12. The process of claim 11 wherein the treatment with sulfuric acid iscarried out for from about 0.5 to about 30 minutes in acid from about40% to about 60% H 80 References Cited UNITED STATES PATENTS 3,189,4046/ 1965 Takizaki et al. 8-116 3,138,802 6/1964 Getchell 8116.3

FOREIGN PATENTS 568,258 1945 Great Britain.

13. The process of claim 12 wherein the curing tem- 15 GEORGE F LESMES,P i E i perature is from to C.

14. The process of claim 12 wherein the precondensate is an acetal.

15. The process of claim 12 wherein the precondensate J. P. BRAMMER,Assistant Examiner US. Cl. X.R.

